Question: $\dfrac{1}{3} - \dfrac{7}{4} = {?}$
Solution: $ = {\dfrac{1 \times 4}{3 \times 4}} - {\dfrac{7 \times 3}{4 \times 3}} $ $ = {\dfrac{4}{12}} - {\dfrac{21}{12}} $ $ = \dfrac{{4} - {21}}{12} $ $ = -\dfrac{17}{12}$